The present invention relates to a self-propelled harvester thresher. More particularly, it relates to a self-propelled harvester thresher which has a threshing and separating device, for example hurdle shaker, as well as a sieve device, with a sieve drum for refining the straw chaff-grain mixture located between the threshing and separating device and the flat sieve device and extending transverse to the transporting direction of the thresher.
Harvester threshers of the abovementioned general type are known in the art. One of such harvester threshers is disclosed, for example in the German published application No. 3,049,534. The mixture straw-chaff and grain is thrown here by means of thrower against a rotatable sieve cylinder with a suction blower located inside the latter. As a result of this, the grains bounce back from the sieve cylinder whereas the chaff and the short straw mixture is held by the suction blower on the sieve cylinder. For releasing the straw-chaff mixture from the sieve cylinder, a part of the cylinder casing is covered from inside, so that here the suction blower cannot apply its suction action. In the region of this cover, a housing is associated with a cylinder casing from outside and a discharging screw is driveably supported in the housing. In such construction considerable problems take place in the sense of adherence and subsequent release of chaff and straw respectively to and from the sieve cylinder in the event of high throughput. In addition, a significant disadvantage of this harvester thresher is that coarser impurities and firmer straw and short straw particles, as well as the grain bounce from the sieve cylinder and cannot be separated. These coarse impurities substantially load the flat sieve device.